After a quarter of a century on the Conservative frontbench he has been appointed by the Queen to the order of the Companions of Honour, which admits only 65 members. He also moves into the private sector with a notable feather in his Tory cap: he was leader of the House of Lords when its reform was deferred for the best part of a generation.

A charming and smooth operator, Strathclyde, 52, would not be so vulgar as to boast that he had personally succeeded in blocking an elected upper house. The reform was killed off last summer by Tory MPs acting, initially at least, with the tacit approval of David Cameron. But Strathclyde's confident prediction that Lords reform would fail before the measure came anywhere near the red benches of his chamber helped to embolden opponents of reform in the House of Commons.

The resignation of Strathclyde, who survived embarrassing revelations about an extramarital affair two years ago, leaves a significant dent in the Tory armoury in the upper house, where the government has suffered 59 defeats since the election. His successor, Lord Hill of Oareford, is a cerebral former political secretary to Sir John Major. He will have to work hard to develop the wily skills that served Strathclyde so well as the first governing Tory leader of the Lords without a majority.

Hill takes over amid deteriorating relations between the coalition partners in the Lords. In a week's time the Liberal Democrats will exact revenge for the killing of Lords reform when they join forces with Labour in the upper house to delay plans to shrink the Commons until after the 2015 general election.

Strathclyde's resignation marks the end of the Tories' last continuous link with the government of Margaret Thatcher. Unlike Kenneth Clarke and Sir George Young, who also served under Thatcher, Strathclyde was the only member of Cameron's government to have served continuously on the Tory frontbench since he was first appointed as a government whip by Thatcher in 1988.

Having notched up another record as the only member of the shadow cabinet and cabinet from 1997, Strathclyde broke through to the front rank when he was the beneficiary of a major internal Tory row over Lords reform in 1998. Viscount Cranborne, now the Marquis of Salisbury, was sacked by William Hague as leader of the Lords in 1998 after he brokered a deal with Labour's communications chief Alastair Campbell over hereditary peers. In return for the first stage of Lords reform, Labour allowed 92 out of around 750 hereditary peers to survive until the second stage of reform.

Strathclyde was appointed to succeed Cranborne and immediately upheld the deal with Campbell. He leaves government confident that "stage two" of Lords reform remains as elusive as ever.